312
P. 9. MEADOWS AND J. I. CAMPBELL
maintain no individual distance from their neighbours (Bagne, 1969) ;
it would be interesting to know of other examples. Crisp’s (1961)
work makes it clear that although barnacle cyprids prefer to have
a space of at least their own body length around them, they settle
more closely together, albeit still spaced out, as density increases.
Presumably the density of settled individuals must eventually reach
a level at which cyprids alighting cannot lind room to settle and so
swim off to find more suitable, and less crowded, surfaces. The
complex ecological effects of this have been discussed by Meadows
(1969) for barnacles, and by Edgar and Meadows (1969) and
McLachlan (1969) who analysed spacing out behaviour in chironomid
(Diptera) larvae in fresh water. Future work might be directed towards
describing the presence or absence of spacing out behaviour in other
marine and freshwater larvae, towards determining its species
specificity, and towards assessing its relation to gregarious behaviour.
Mobile adult invertebrates appear to space out in the same way
as do the larvae of sedentary marine invertebrates (Pearl, 1903;
Bovbjerg, 1960; Connell, 1963). Bovbjerg (1953, 1964) using simple but
elegant experiments, has for some while been concerned with the
analysis of aggressiveness and its relation to spacing out and dispersal
in adult aquatic invertebrates. He contrasts species that show
aggressive behaviour to their own species and disperse more quickly as
the population density increases, with species showing no aggressiveness which disperse at a rate independent of density. Examples of the
former are the intertidal crab Pachygrapsus crassipes Randall
(Bovbjerg, 1960) and the freshwater crayfish Cumburus alleni Faxon
(Bovbjerg, 1959), while examples of the latter are the freshwater snail
Campelomu decisum Say (Bovbjerg, 1962a) and the freshwater amphipod Gammarus pseudolimruzeus Bonsfield (Clampitt, unpublished
results in Bovbjerg, 1964). However, before these generalizations can
be fully accepted more work is needed, and Bovbjerg (1964) himself
realizes this.
Aggressive behaviour, which will of course tend to lead to a spaced
out distribution, has been studied in a number of other adult
invertebrates, but usually from a purely ethological point of view rather
than by trying t o correlate the ecological distribution of a species with
its behaviour (Reese, 1964). Characteristic encounters occur when
various Crustacea (Douglis, 1946; Crane, 1958; Fielder, 1965; Cameron,
1966; Hazlett, 1966; Dingle and Caldwell, 1969) meet each other, and
also when burrowing worms (Nereis: Clark, 1959) and Crustacea
(Erichthonius: Connell, 1963; Mictyris: Cameron, 1966; Corophium:
Meadows and Reid, 1966; Gonoduetylus: Dingle and Caldwell, 1969)
P. 9. MEADOWS AND J. I. CAMPBELL
maintain no individual distance from their neighbours (Bagne, 1969) ;
it would be interesting to know of other examples. Crisp’s (1961)
work makes it clear that although barnacle cyprids prefer to have
a space of at least their own body length around them, they settle
more closely together, albeit still spaced out, as density increases.
Presumably the density of settled individuals must eventually reach
a level at which cyprids alighting cannot lind room to settle and so
swim off to find more suitable, and less crowded, surfaces. The
complex ecological effects of this have been discussed by Meadows
(1969) for barnacles, and by Edgar and Meadows (1969) and
McLachlan (1969) who analysed spacing out behaviour in chironomid
(Diptera) larvae in fresh water. Future work might be directed towards
describing the presence or absence of spacing out behaviour in other
marine and freshwater larvae, towards determining its species
specificity, and towards assessing its relation to gregarious behaviour.
Mobile adult invertebrates appear to space out in the same way
as do the larvae of sedentary marine invertebrates (Pearl, 1903;
Bovbjerg, 1960; Connell, 1963). Bovbjerg (1953, 1964) using simple but
elegant experiments, has for some while been concerned with the
analysis of aggressiveness and its relation to spacing out and dispersal
in adult aquatic invertebrates. He contrasts species that show
aggressive behaviour to their own species and disperse more quickly as
the population density increases, with species showing no aggressiveness which disperse at a rate independent of density. Examples of the
former are the intertidal crab Pachygrapsus crassipes Randall
(Bovbjerg, 1960) and the freshwater crayfish Cumburus alleni Faxon
(Bovbjerg, 1959), while examples of the latter are the freshwater snail
Campelomu decisum Say (Bovbjerg, 1962a) and the freshwater amphipod Gammarus pseudolimruzeus Bonsfield (Clampitt, unpublished
results in Bovbjerg, 1964). However, before these generalizations can
be fully accepted more work is needed, and Bovbjerg (1964) himself
realizes this.
Aggressive behaviour, which will of course tend to lead to a spaced
out distribution, has been studied in a number of other adult
invertebrates, but usually from a purely ethological point of view rather
than by trying t o correlate the ecological distribution of a species with
its behaviour (Reese, 1964). Characteristic encounters occur when
various Crustacea (Douglis, 1946; Crane, 1958; Fielder, 1965; Cameron,
1966; Hazlett, 1966; Dingle and Caldwell, 1969) meet each other, and
also when burrowing worms (Nereis: Clark, 1959) and Crustacea
(Erichthonius: Connell, 1963; Mictyris: Cameron, 1966; Corophium:
Meadows and Reid, 1966; Gonoduetylus: Dingle and Caldwell, 1969)